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Author Smith, Devin H.; Gillett, Geoff; de Almeida, Marcelo P.; Branciard, Cyril; Fedrizzi, Alessandro; Weinhold, Till J.; Lita, Adriana; Calkins, Brice; Gerrits, Thomas; Wiseman, Howard M.; Nam, Sae Woo; White, Andrew G.
Title Conclusive quantum steering with superconducting transition-edge sensors Type Journal Article
Year 2012 Publication (down) Nature Communications Abbreviated Journal Nat. Comm.
Volume 3 Issue 625 Pages 6
Keywords fromIPMRAS
Abstract Quantum steering allows two parties to verify shared entanglement even if one measurement device is untrusted. A conclusive demonstration of steering through the violation of a steering inequality is of considerable fundamental interest and opens up applications in quantum communication. To date, all experimental tests with single-photon states have relied on post selection, allowing untrusted devices to cheat by hiding unfavourable events in losses. Here we close this 'detection loophole' by combining a highly efficient source of entangled photon pairs with superconducting transition-edge sensors. We achieve an unprecedented ~62% conditional detection efficiency of entangled photons and violate a steering inequality with the minimal number of measurement settings by 48 s.d.s. Our results provide a clear path to practical applications of steering and to a photonic loophole-free Bell test.
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Call Number RPLAB @ gujma @ Serial 768
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Author Ghali, Mohsen; Ohtani1, Keita; Ohno, Yuzo; Ohno, Hideo
Title Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field Type Journal Article
Year 2012 Publication (down) Nature Communications Abbreviated Journal Nat. Comm.
Volume 3 Issue 661 Pages 6
Keywords fromIPMRAS
Abstract Semiconductor quantum dots are potential sources for generating polarization-entangled photons efficiently. The main prerequisite for such generation based on biexciton-exciton cascaded emission is to control the exciton fine-structure splitting. Among various techniques investigated for this purpose, an electric field is a promising means to facilitate the integration into optoelectronic devices. Here we demonstrate the generation of polarization-entangled photons from single GaAs quantum dots by an electric field. In contrast to previous studies, which were limited to In(Ga)As quantum dots, GaAs island quantum dots formed by a thickness fluctuation were used because they exhibit a larger oscillator strength and emit light with a shorter wavelength. A forward voltage was applied to a Schottky diode to control the fine-structure splitting. We observed a decrease and suppression in the fine-structure splitting of the studied single quantum dot with the field, which enabled us to generate polarization-entangled photons with a high fidelity of 0.72 ± 0.05.
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Call Number RPLAB @ gujma @ Serial 769
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Author Grotz, Bernhard; Hauf, Moritz V.; Dankerl, Markus; Naydenov, Boris; Pezzagna, Sébastien; Meijer, Jan; Jelezko, Fedor; Wrachtrup, Jörg; Stutzmann, Martin; Reinhard, Friedemann; Garrido, Jose A.
Title Charge state manipulation of qubits in diamond Type Journal Article
Year 2012 Publication (down) Nature Communications Abbreviated Journal Nat. Comm.
Volume 3 Issue 729 Pages 6
Keywords fromIPMRAS
Abstract The nitrogen-vacancy (NV) centre in diamond is a promising candidate for a solid-state qubit. However, its charge state is known to be unstable, discharging from the qubit state NV- into the neutral state NV0 under various circumstances. Here we demonstrate that the charge state can be controlled by an electrolytic gate electrode. This way, single centres can be switched from an unknown non-fluorescent state into the neutral charge state NV0, and the population of an ensemble of centres can be shifted from NV0 to NV-. Numerical simulations confirm the manipulation of the charge state to be induced by the gate-controlled shift of the Fermi level at the diamond surface. This result opens the way to a dynamic control of transitions between charge states and to explore hitherto inaccessible states, such as NV+.
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Call Number RPLAB @ gujma @ Serial 770
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Author Pernice, W. H. P.; Schuck, C.; Minaeva, O.; Li, M.; Goltsman, G. N.; Sergienko, A. V.; Tang, H. X.
Title High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits Type Journal Article
Year 2012 Publication (down) Nat. Commun. Abbreviated Journal Nat. Commun.
Volume 3 Issue Pages 1325 (1 to 10)
Keywords waveguide SSPD
Abstract Ultrafast, high-efficiency single-photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. However, imperfect modal matching and finite photon absorption rates have usually limited their maximum attainable detection efficiency. Here we demonstrate superconducting nanowire detectors atop nanophotonic waveguides, which enable a drastic increase of the absorption length for incoming photons. This allows us to achieve high on-chip single-photon detection efficiency up to 91% at telecom wavelengths, repeatable across several fabricated chips. We also observe remarkably low dark count rates without significant compromise of the on-chip detection efficiency. The detectors are fully embedded in scalable silicon photonic circuits and provide ultrashort timing jitter of 18 ps. Exploiting this high temporal resolution, we demonstrate ballistic photon transport in silicon ring resonators. Our direct implementation of a high-performance single-photon detector on chip overcomes a major barrier in integrated quantum photonics.
Address Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA
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ISSN 2041-1723 ISBN Medium
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Notes PMID:23271658; PMCID:PMC3535416 Approved no
Call Number Serial 1375
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Author Sclafani, M.; Marksteiner, M.; Keir, F. M. L.; Divochiy, A.; Korneev, A.; Semenov, A.; Gol'tsman, G.; Arndt, M.
Title Sensitivity of a superconducting nanowire detector for single ions at low energy Type Journal Article
Year 2012 Publication (down) Nanotechnol. Abbreviated Journal Nanotechnol.
Volume 23 Issue 6 Pages 065501 (1 to 5)
Keywords NbN SSPD, SNSPD, superconducting single ion detector, SSID, SNSID
Abstract We report on the characterization of a superconducting nanowire detector for ions at low kinetic energies. We measure the absolute single-particle detection efficiency eta and trace its increase with energy up to eta = 100%. We discuss the influence of noble gas adsorbates on the cryogenic surface and analyze their relevance for the detection of slow massive particles. We apply a recent model for the hot-spot formation to the incidence of atomic ions at energies between 0.2 and 1 keV. We suggest how the differences observed for photons and atoms or molecules can be related to the surface condition of the detector and we propose that the restoration of proper surface conditions may open a new avenue for SSPD-based optical spectroscopy on molecules and nanoparticles.
Address Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna, Vienna, Austria
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Language English Summary Language Original Title
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ISSN 0957-4484 ISBN Medium
Area Expedition Conference
Notes PMID:22248823 Approved no
Call Number Serial 1380
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